Myocarditis can cause ventricular wall thickening due to myocardial edema. If the condition improves, the ventricular wall thickening should gradually decrease; a persistent thickening of the patient's ventricular wall indicates the coexistence of hypertrophic cardiomyopathy (HCM) and myocarditis. A 30-year-old man was referred to our hospital with continuous chest pain accompanied by profuse sweating. He suffered from fever for two days (the maximum body temperature: 38 °C) and the conditions improved following the use of antipyretics as self-administered medication before admission. Electrocardiogram exhibited ST-segment elevation in leads I and avL, and ST-T wave changes in leads II, III, avF, and V1-V6. Marked elevation of cardiac troponin I was found on laboratory testing. Respiratory tract infection testing showed negative results. A TORCH screen revealed positive herpes simplex virus (HSV), rubella virus (RV), and cytomegalovirus (CMV) IgG but all with negative IgM titer. Ultrasonic echocardiography showed thickness of the interventricular septum (17 mm) and diffuse left ventricular (LV) hypokinesia, without LV outflow tract obstruction. After consultation with the cardiology team, a diagnosis of myocarditis with HCM was made. Patients with myocarditis should be alerted to the possibility of HCM when there is persistent ventricular wall thickening.